Consistent searches for SMEFT effects in non-resonant dilepton events

Abstract

Employing the framework of the Standard Model Effective Field Theory, we perform a detailed reinterpretation of measurements of the Weinberg angle in dilepton production as a search for new-physics effects. We truncate our signal prediction at order 1/Λ 2 , where Λ denotes the new-physics mass scale, and introduce a theory error to account for unknown contributions of order 1/Λ 4 . Two linear combinations of four-fermion operators with distinct angular behavior contribute to dilepton production with growing impact at high energies. We define suitable angular observables and derive bounds on those two linear combinations using data from the Tevatron and the LHC. We find that the current data is able to constrain interesting regions of parameter space, with important contributions at lower cutoff scales from the Tevatron, and that the future LHC data will eventually be able to simultaneously constrain both independent linear combinations which contribute to dilepton production.

Flavor Constraints from Unitarity and Analyticity

“…1111 c e;1 2112 > jc e;1 1112 j 2 , so taking c e;1 2112 ∼ c e;1 1111 ¼ Λ −4 , there is a flavor conserving effectpotentially observable at a collider-that cannot be decoupled:Λ > Λ. Collider measurements may be less sensitive than rare decay searches, but can be enhanced through the higher-dimension operator interference with the SM. For fermion pair production at LEP, recast dimension-6 limits require Λ ≳ 500 GeV [31,32], in violation of our bounds. These estimates are not a dedicated analysis, but highlight that collider constraints, together with our bounds, already impact flavor violation probes.…”

Matching for FCNC effects in the flavour-symmetric SMEFT

“…Loop corrections to very precisely measured and particularly interesting processes have been calculated [20][21][22][23][24][25][26][27][28][29][30][31][32]. LHC searches have also been interpreted in the SMEFT, with techniques to address the unique theoretical errors inherent in high energy searches for EFT effects recently developed [33,34]. Ultimately, all of these contributions will need to coalesce into a fully global fit of the SMEFT Wilson coefficients and cutoff scale, as only then will it be possible to truly understand the conservative constraints which can be imposed on an arbitrary model through matching to the SMEFT and comparison of a given parameter point to the likelihood associated with all the relevant measurements.…”

Dijets at Tevatron cannot constrain SMEFT four-quark operators

“…A consistent and conservative technique to derive bounds on the SMEFT from collider searches has been developed in [32] and further applied in [33]; it utilizes the well-understood techniques of perturbation theory in the context of the expansion in inverse powers of the new physics scale Λ. There are two important steps which, prior to the introduction of this technique, have not been consistently performed in searching for higher-dimension effects in the SMEFT or any other EFT-based framework for model-independent new physics parameterization in collider searches.…”